Field of the Invention
The present invention relates to a control system for a well, producing oil and gas by the gas lift plunger method, wherein a plunger or "rabbit" lifts all the fluids (oil, gas and water) out of the well tubing by the application of pressurized gas underneath the "rabbit" from the oil formation or from the well casing.
The standard operating procedure to produce gas or oil from wells utilizing a gas lift plunger comprises operating on a specifically designated timed on and off cycle. During the off cycle, the well is in an idle position storing the oil and gas and other fluids above the "rabbit" or plunger. Once the designated time for the duration of the off cycle is reached, the controller actuated by the timing device opens a master flow valve which increases the gas pressure underneath the plunger by increasing the gas flow from the earthen formation or from gas supplied through the well casing to provide upward movement of the plunger through the well tubing. The upward movement of the plunger pushes all of the oil or other fluids in the tubing which have accumulated above the plunger to the top of the well. While the well is operated on the on cycle, the plunger continues pushing the oil or other fluids up through and out of the well tubing. When the tubing reaches the off position, which time has been preset, the gas flow underneath the plunger is terminated, along with the upward movement of the plunger and the production of oil and gas from the well. The presetting of on and off cycle duration times often results in inefficient oil production, as the time it takes for the plunger to reach the top of the well is varied depending upon the amount and viscosity of the oil or other fluids pushed up the well. In some instances, the plunger has not reached the top of the well when the preset time for the on cycle has ended, and in other instances the plunger has reached the top of the well before the on cycle is over. Besides timing devices, pressure sensing devices have also been used to initiate the on and off cycle of wells operated by the gas lift plunger method.
The present invention provides for a device which senses the proximity of the "rabbit" at the top of the well, which device is utilized to trigger the control mechanism to initiate the off cycle. Since the off cycle is initiated only when the "rabbit" has reached the top of the well, all the oil or other fluids which have been collected from the formation are brought to the top of the well and collected. The sensing device enables the efficient production of oil wells, significantly reducing the amount of waste gas used to drive the plunger or "rabbit" up the well tubing.